AutoMigrate creating different unique Index on subsequent runs

[cabeedelhertz]

GORM Playground Link

go-gorm/playground#608

Description

I have an existing database and consistently run Automigrate but after upgrading my gorm version from 1.28.3, the automigrate is creating different unique indexes than the ones I have defined and already exist in my database.

To reproduce, pull this branch and run GORM_DIALECT=postgres go test. This should work and pass tests. But if you run it again, it will fail to make migrations because it is trying to create a uniqueIndex and uniqueConstraint that doesn't have the same name or where clause as the unique index that I defined:
ERROR: could not create unique index "idx_users_description" (SQLSTATE 23505)

After the initial run of AutoMigrate the unique indexes that I defined are correctly created:

But after the next time I run AutoMigrate, it created new unique indexes with a different name and without the where clause:

I can only get to the state of the second picture if I don't have any data that conflicts the where clause of the unique index of the description column. In my use case, I have a table with a unique index with a where deleted_at is NULL condition but now that my AutoMigrate behaves differently, I cannot run migrations.

Did something change with how AutoMigrate handles unique indexes?

[a631807682]

What version of postgres are you using? This seems to be an error caused by the handling of the index name, but in fact I cannot reproduce the wrong creation of this index from the link you provided.

[cabeedelhertz]

What version of postgres are you using? This seems to be an error caused by the handling of the index name, but in fact I cannot reproduce the wrong creation of this index from the link you provided.

using gorm.io/driver/postgres v1.5.2

[cabeedelhertz]

fact I cannot reproduce the wrong creation of this index from the link you provided.

And yeah sorry with the given tests you can't actually create the wrong index because the tests insert conflicting data. But you should see errors that it is failing to create those indexes. I just included the "wrong" index in the description to show what autoMigrate is trying to create

[a631807682]

refer to #6381 (comment)
At present, the redundant index can only be deleted manually.

if DB.Migrator().HasIndex(&User{}, "users_description_key") {
	DB.Exec(`ALTER TABLE ? DROP CONSTRAINT ?`,
		clause.Expr{SQL: "users"},
		clause.Expr{SQL: "users_description_key"},
	)
}

[cabeedelhertz]

Yeah that is what I've been doing to fix it but gorm shouldn't be creating that index in the first place. Do we know why it gets created and can we get a fix the next release?

[a631807682]

#6381 (comment)